not really...
php goes to work before any thing is sent to the browser (assuming no [man]flush/man)...
each character is 8-bytes (thats pretty standard) so you can just count up how many characters your final output is...
however the server also takes your data when php is done with it and sends it wrapped in a http response... this php cannot have direct knowledge of but if you know your server it can be predicted in certian situations...
you could use the [man]ob_start[/man] functions and then before you send it just count the characters...
you might also want to take into consideration the images and image sizes.... as they will not actually be sent with the request but will also have to be gotten after by the browser... so maybe you will count htat...
punchline:
php is ill suited for doing this..
however maybe someone smarter knows a way to do this...
